S3.5.8 For the adult
Density
Why does oil float on water, and why does a stone sink?
What this chapter teaches
Density is how much mass is packed into each cm³. A thing floats in a liquid if it is less dense than the liquid, and sinks if it is denser. Heavy things do not always sink: size and mass alone do not decide it.
Three questions to ask
There is no one right wording. Listen for the idea.
- Why do you think a big log floats but a small stone sinks?
- If you pour oil on water, which one goes on top, and why?
- How could you find the volume of a stone that is not a neat shape?
After the chapter, the learner can
- Explain density as how much mass is packed into a space
- Explain why oil floats on water and a stone sinks
- Calculate density from mass and volume
What they copy into their notebook
Density is mass divided by volume, in g/cm³. A thing floats if it is less dense than the liquid and sinks if it is denser. Water is about 1 g/cm³.